This invention relates to a method of applying a coating solution such as photographic emulsion or magnetic agent to both sides of an elongated flexible support (hereinafter referred to as "a web") in order to manufacture photographic photo-sensitive materials such as photographic films and photographic print paper, photo-engraving materials, magnetic recording materials such as magnetic sound recording tapes and pressure-sensitive copying sheets, heat-sensitive recording sheets, or the like.
In a conventional method of successively coating both sides of a web is as follows: After one of the two sides of a web is coated, the coated side is supported in a non-contact manner, and then the other side is coated as shown in, for example, U.S. Pat. No. 4,455,327.
However, the conventional method suffers from a difficulty that, as the coating speed increases, the air, being entrained on the surface of the web running at a high speed, remains between the coating solution and the web, thus making the coated surface defective.
One of methods for overcoming this difficulty is as follows: Namely the affinity of a coating solution to a web is increased. More specifically, for instance the density of the coating solution is decreased (in the case of a coating solution containing gelatin, the density of gelatin is decreased) so that the viscosity of the coating solution on the web is decreased. However, the method is still disadvantageous in that the drying load is increased, so that the employment of the method is limited.